Watching zpool iostat it does read all data on both disks in a mirrored
pair.

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Logically, it would not make sense not to verify all redundant data.
The point of a scrub is to ensure all data is correct.

On 2012-10-25 10:25, Jim Klimov wrote:

Hello all,
I was describing how raidzN works recently, and got myself wondering:
does zpool scrub verify all the parity sectors and the mirror halves?
That is, IIRC, the scrub should try to read all allocated blocks and
if they are read in OK - fine; if not - fix in-place with redundant
data or copies, if available.
On the other hand, if the first tested mirror half/block copy/raidzN
permutation has yielded no errors, are other variants still checked?
The descriptions I've seen so far put an emphasis on verifying all
copies of the blocks and probably all the mirror halves - perhaps
because these examples make it easier to describe the concept.
I don't think I saw a statement that for raidzN blocks all of the
combinations are verified to work (plain userdata sectors, and parity

permutations with these sectors). Can someone in the know say "yes"?
;)